Protein drugs are believed to be one of the fastest growing sectors of the pharmaceutical industry, but development is often hindered by the inherent instability of these large, complex molecules. Protein drugs having an Fc domain are particularly useful in treating diseases. However, it has been reported that protein drugs having an Fc domain exhibit low stability, because among other things, such protein drugs reportedly homodimerize or aggregate, adopt non-active or less active conformations, and/or denature by unfolding, partially unfolding, or improperly refolding. It has also been reported that such protein drug stability may occur during storage, and/or is accelerated by agitation, especially at temperatures at or above ambient. Accordingly, such protein drugs are stored at refrigerated temperatures, and a cold-chain is reportedly required to be maintained from the point of manufacture to the point of administration.
Particularly in the case of underdeveloped countries, such as Sub-Saharan Africa and Latin America, protein drugs in the form of vaccines have been an important tool in the arsenal of combating diseases. However, many of those protein formulations including vaccines must be kept refrigerated in order to maintain the stability of the drugs during storage or transportation until administered. Not surprisingly, in many those countries most in need of such protein drugs, the availability of electricity is either sporadic or non-existent, making refrigeration of the drugs unreliable or not possible. Protein drugs must be formulated to preserve stability during manufacturing, shipping and storage so that a safe and fully potent drug is administered to the patient. Administering a partially degraded protein drug may increase the risk for life-threatening side effects, particularly if protein aggregates are present. Current stabilization strategies include adding excipients, refrigerating the product, or producing a dried form. However, for a given protein, the appropriate stabilizing strategy is typically identified by trial-and-error and by experience, a process that can take years at considerable cost. An inability to stabilize a protein may preclude commercialization, so that a promising drug is lost to the market and to the patients who need it. It is therefore understood that a need exists for protein drug formulations, and storage that is less susceptible to these and other limitations.
It has also been reported that protein drugs may have insufficiently long in vivo half-life for optimal treatment efficacy. Covalent modification of protein drugs, that includes covalent addition of polyethylene glycols, also referred to as PEGylation, has been reported as a possible solution to the observed short half-life (see, for example, PEGylation of therapeutic proteins in Biotechnol J 5:113-128 (2010)). It is therefore understood that a need also exists for protein drug formulations that exhibit longer in vivo half-life, including protein drug formulations that do not require a covalent modification of the protein drug.
It has been discovered that proteins having an Fc domain exhibit higher stability when mixed with one or more of the polyamino acid ligands described herein. It has also been discovered herein that protein drugs are stabilized by binding to polyamino acid ligands. It is to be understood that as used herein, polyamino acid ligands includes peptide ligands of varying lengths, such as oligopeptide ligands and polypeptide ligands, and also includes protein ligands. Without being bound by theory, it is believed herein that such mixtures of proteins having an Fc domain and the polyamino acid ligands described herein form complexes that may stabilize the active conformation, decrease the denaturation, and/or decrease the homodimerization or aggregation of the proteins having the Fc domain. Without being bound by theory, it is also believed herein that one possible mechanism of decreasing aggregation of the protein having an Fc domain is due to the creation of a steric barrier upon formation of the complex. The steric barrier may generally or indirectly decrease or prevent the homodimerization or aggregation by crowding the sites of interaction that would be used by the proteins having an Fc domain to form homodimers or aggregates. Without being bound by theory, it is also believed herein that one possible mechanism of decreasing aggregation of the protein having an Fc domain is due to a competitive interaction between the one or more ligands and the region of the protein having an Fc domain that initiates, stabilizes, and/or forms the dimer or aggregate. The competitive interaction may generally or directly decrease or prevent the homodimerization or aggregation by competitively blocking the sites of interaction that would be used by the proteins having an Fc domain to form homodimers or aggregates. Without being bound by theory, it is also believed herein that one possible mechanism of decreasing aggregation of the protein having an Fc domain is due to the separation in space of complexes in configurations of the complexes that are attached to a solid support.
Described herein are methods for stabilizing protein drugs using one or more polyamino acid ligands as binding agents. These methods exploit the large and structurally diverse pool of natural ligands to develop new stabilizing materials for protein drugs, and are believed to have more general applicability to a wide variety of protein drugs.
In one embodiment, pharmaceutical compositions that include a drug comprising a protein having an Fc domain, and one or more polyamino acid ligands for the protein are described herein. In another embodiment, the composition is a solution. In another embodiment, the composition is a suspension. In another embodiment, the composition is a solid, such as a solid prepared from a solution and/or suspension described herein. The solid may be reconstituted to prepare a solution and/or suspension described herein. In another embodiment, the composition includes a solid support comprising the one or more polyamino acid ligands covalently attached thereto.
In another embodiment, the compositions may be used as a means of storage of the drug comprising a protein having an Fc domain. In another embodiment, the compositions may be administered as a drug composition. In another embodiment, the protein having an Fc domain is released or separated from the one or more polyamino acid ligands prior to administration.